Cant-indicating mechanism



March 10, 1959 R. A. VISSING 2,876,546

CANT-INDICATING MECHANISM Filed April 13, 1953 3 Sheets-Sheet 1 iii iii

FIGQ FIGS INVENTOR.

- fioya/AV/ssing March 10, 1959 R. A. VISSING CANT-INDICATING MECHANISM Filed Apfil 1:5, 1953 3 Sheets-Sheet 2 INIZVjNTOR.

March 10, 1959 v ss 2,876,545

CANT-INDICATING MECHANISM Filed April 13, 1953 s Sheets-Sheet s -r l I! I N VEN TOR.

nited States This invention relates to a mechanism for indicating the cant of a gun, or like device, utilizing a telescope for sighting purposes.

The bore of modern rifle and pistol barrels is inclined upwardly when a gun is in a normal firing position, to compensate for the gravitational elfect on a bullet as it travels along its trajectory. Accordingly, if the gun is canted, or turned about its line of sight as an axis, the accuracy of the gun will beseriously afiected. An object of this invention, therefore, is to provide a cant-indicating device that will indicate instantly to the gunner whether his gun is canted, and also how to adjust the position of the gun to correct for such canting.

Another object of the invention is to provide a cant indicator for telescopic sights for guns which may be wholly disposed'in the telescope.

Another object of the invention is to provide a cant indicator which is notafiected when making adjustments for windage and elevation.

Another object of the invention is the provision of cant-indicator means that will in effect project a true level and vertical line through space for an indefinite distance.

Another object is to provide a cant indicator which clearly indicates canting when shooting either uphill or downhill.

Another object of the invention is to provide a cant indicator which may be installed as a unit in a telescopic sight by anyone reasonably skilled in working with his hands.

A further object of the invention is to provide a cant indicator which does not require an unslightly housing external to the telescope.

Another object of the invention is to provide a cant indicator which does not interfere with the field of vision of the telescope with which it is used.

Another object of the invention is the provision of a cant indicator having a swinging pendulum whose oscillation is quenched by the generation of eddy currents.

Another object of the invention is the provision of a novel cant indicator utilizing a weighted pendulum supported by pivotal bearings, with novel means interposed between the weight on the pendulum and the bearings for absorbing shock to prevent damage to the bearings due to the recoil of the gun when the latter is fired.

Another object of the invention is the provision of a cant indicator utilizing a pendulum, having novel means for limiting the amplitude of the pendulum oscillation.

Other'objects and advantages of the invention will become more apparent upon reference to the accompanying drawings in which:

Figure 1 is a fragmentary longitudinal, sectional view through a conventional telescopic sight utilizing a cant indicator embodying the present invention.

Figure 2 is a side elevation of the pendulum of the cant indicator.

Figure 3 is an end view of the construction shown in Figure 2.

2,876,546 Patented Mar. .10, 1959 Figure 4 is an end view of Figure 1.

Figure 5 is an enlarged fragmentary view of the cant indicating mechanism showing details of construction.

Figure 6 is an end view of the cant-indicating mechanism.

Figure 7 shows a modifiedform of the cant-indicating mechanism in a conventional telescope.

Figures 8, 9, 10 and 11 are views showing details "of construction of the modified form of the invention.

Figure 1-2 shows a further modification of a cant-indicating mechanism disposed in a conventional telescopic sight.

Figures 13 and 14 'are side'andfront elevational views of the indicator mechanism shown in Figure 12.

Figure 15 is a sectional view taken substantially along the line 1515 of Figure 7.

Referring particularly to the drawings, the invention is shown embodied in a conventional telescopic .sight. For purposes of illustration the telescopic sight shown is of a conventional type comprising a tube 10, an inner sleeve 11, a yoke 12, attaching screw 14, an elevationadjusting screw 15, and a windage-adjusting screw 16, together with lock nuts 18 and '19 mounted respectively on the adjusting screws 15 and 16.

The cant-indicating mechanism in this embodiment of the invention includes a fiat spring 20 to hold a reticule cage 22 firmly against the inner ends of the adjusting screws 15 and 16. The spring 20 is secured to the sleeve 11 by a screw 21. The reticule cage 22 is annular in shape and of slightly smaller diameter than the bore of the tube 10.

The cage encloses the magnetic pendulum 23 which may oscillate transversely of the axis of the cage. Brazing or soldering 25 secures the reticule cage 22 to the end of the spring 20. Essentially the reticule cage is a pendulum support and to this end the cage has a circular opening or slot 26 which is wider than the pendulum 23 so that the latter may oscillate without contacting the walls defining the slot. At its top 24, where the slot does not extend, the cage has a pair of conical bearings, one of which, designated 28, is formed in the end of a set screw 29 threadedv into the cage in alignment with the bearing 27. These conical bearings are for the pivot 30 of the pendulum 23, which pivot is pointed at both ends to provide a small contact area at said ends with the bearing.

A pair of mutually perpendicular crosshairs 31 and 3.2 are secured in the conventional manner to one end of the reticule cage. .As shown, the crosshair 31 is a vertical reference crosshair and the crosshair 32 is a horizontal reference crosshair.

The pendulum 23 is a permanent magnet With poles at A and B as shown in Figure 2. The pendulum 23 is generally ring or annular shaped, and is secured in any conventional manner to the pivot 30 by which it is supported so as to swing freely through a limited arc within said slot or groove 26.

Stops 33 and 34 (see Figure 3) rigid with the periphery of the pendulum 23, adjacent the pivot and on either side thereof, are adapted to strike the enclosing wall (see Figure 4 of the cage as the pendulum reaches either limit of swing.

A cant hair 35 is secured at its lower end by cement 37 to the bottom portion of the pendulum 23 and projects upwardly from the secured end in a true vertical line, but preferably terminates short of the horizontal plane of the crosshair 32. As shown the fixed end of cant hair 35 and the free end of the cant hair 35 and the pivotal bearings are in alinement.

In Figure 4 the cant hair .35 does not coincide with the vertical crosshair 31. This indicates that the rifle is canted to the left. The mass of the pendulum may be increased by widening the lower end thereof as indicated at 36 in Figure 5.

The use of the device will be apparent from the foregoing description, but may be summarized briefly as follows:

Assume that the indicating device is installed in a telescopic sight of a gun and that the crosshairs appear as in Figure 6. The gunner knows, under these conditions, that his gun is canted to the left and that he must turn or rotate the gun around the line of sight as an axis indicated herein as OA until the cant hair 35 disappears by visually coinciding with the vertical crosshair 31.

Because the construction of the pendulum and pivot bearings is such that friction is reduced to a minimum in order to make the pendulum sensitive, it is apparent that the pendulum will tend to oscillate for a considerable period of time. Provision is made for dampening the amplitude of the oscillation and quickly bringing the pendulum to test. To this end the eddy currents set up by the magnetic pendulum in the reticule cage which closely surrounds the pendulum are in such a direction as to oppose the motion producing them, in accordance with Lenzs law. Thus it will be seen that the pendulum cannot swing freely indefinitely, but must come to a rest very quickly.

It is apparent, also, from the foregoing that the cant indicating mechanism may be installed as an integral unit in the telescopic sight with a minimum of time and effort.

Referring now to Figures 7, 8, 9, l0, l1 and 15, there is shown another embodiment of the invention. In this embodiment of the invention the cant-indicating mechanism includes a reticule support 40, a pendulum 41, and a cant indicator 42 mounted in a conventional telescope having objective lenses 43, ocular lenses 44, and an erecting lens 44a defining an optical system having a field of vision, or view. The lenses may be of conventional construction and should provide for magnification in a conventional manner.

The reticule support 40 (see Figure comprises a generally annular disc member 40a having mutually perpendicular crosshairs 45 and 46. Each crosshair has its opposite ends fixedly'secured to the periphery of the disc 40a at diametrically opposed positions. The crosshair 45 is a vertical crosshair and the crosshair 46 is a horizontal crosshair. As best seen in Figures 8 and 15 the ends of the crosshair 46 are received in diametrically opposed V-shaped notches 46a opening on the outside face of the disc-shaped member 40a. Any suitable conventional means may be used for securing the ends of the crosshairs in position in said notches. As will be seen in Figure 8, the depth of the notches is such that the inner ends ofvthe notches 46a are adjacent the opposite inside face of the disc-shaped member 40a. This construction permits the crosshairs to be in relatively closely-spaced relation with the cant indicator 42.

The pendulum 41 in this instance is formed by arcuate, downwardly-curving upper arm portions 47 and 48, depending straight portions 49 and 51, and arcuate, upwardly-curving lower arm portions 52 and 53 integrally interconnected together, as shown in Figure 9, to define a generally annular pendulum in substantially parallel relation with the plane of the crosshairs. The pendulum has a central opening 50b of such size and shape (herein shield-shaped) that the arm portions 47 and 48, the depending straight portions 49 and 51, and the arm portions 52 and 53 are all out of the field of vision or line of sight through the telepscope. In this embodiment of the invention the pendulum 41 is of one-piece construction and may be formed from phosphor-bronze material.

The support for the pendulum includes a shaft 69 having pointed ends 54 and 56, and spaced bearings 50 and 50a shaped to receive and supportthe ends of the shaft 60. Preferably these hearings are jewel bearings rigidly mounted. As shown, the bearing 50a is mounted in the end of a machine screw 57 extending through a threaded opening formed at the top of the disc 40a. The bearing 50 is supported in the end of a machine screw 58 extending through a threaded opening in an annular disc 59 spaced from the disc 40a and in parallel relation therewith and with the pendulum 41. A locknut 55 on the machine screw 57 may be utilized to hold the hearings in a desired adjusted relation. The screw 58 should preferably be first secured in position as by cement or solder.

An arcuate-shaped bridging portion 61 interconnects the top half portions of the disc 40a and the annular support disc 59. In effect, the discs 40a and 59 and the bridging portion 61 define a cage or enclosure for the pendulum, as best seen in Figure 8. A weight 62 is mounted on the pendulum at the point of juncture between the lower arms 52 and 53 as seen in Figure 9. This concentrates the mass of the pendulum at the lower end thereof away from the bearings 50 and 50a and effects the proper operation of the pendulum. The weight 62 is preferably in the form of a permanent magnet; the purpose of this is to provide an oscillation dampening means to quickly bring the pendulum to its rest position as described herein.

It has been found that the weighted pendulum may stress the bearings 50 and 50a so much that the latter are damaged when the gun is fired. To limit the shock and to minimize the damage to the bearings, the upper arm portions 47 and 48, and the straight portions 51 and 49 are of a reduced cross sectional area to provide flexibility to the pendulum and in turn, means for absorbing the shock as a result of recoil of the gun. With this construction it has been found that damage to the bearings has been minimized, if not entirely eliminated.

The cant indicator 42 per se in this embodiment of the invention comprises a glass filament approximately ,4 to inch in diameter. The filament in this instance has a fixed end 64 and a free end 66. The fixed end is anchored to the pendulum as by securing it to the weight 62 and the free end is positioned to extend partially across the field of vision, but preferably short of the optical axis, as seen in Figure 9. The free end is also positioned to be in alinement with the fixed end 64 and the pivotal bearings 50 and 50a. With this construction it will be seen that the cant indicator 42 is visually associated with the vertical crosshair 45 so as to indicate cant as previously described. It has been found that a glass filament is one of the best materials for this purpose inasmuch as it is highly elastic and is not readily distorted upon assembly of the cant indicating mechanism or sudden jarring of a telescope.

The cant indicating mechanism may be mounted in the telescope tube 68 in any desired manner. As shown in Figure 7 and 8 the disc 59 is attached to a semitubular member 69 having a tongue portion 71 extending outwardly from the periphery of the semi-tubular member 69 to define a spring. The semi-tubular member 69 is shaped to nest in a spring saddle 72 secured in the telescope tube 68. Conventional elevation-adjusting screw 73 and a windage-adjusting screw 74 at right angles to each other and extending through the walls of the tube 68 engage an upstanding arcuate rib 76a on the bridging portion 61 of the pendulum cage. Covers, or caps, 73a and 74a are provided for screws 73 and 74, respectively. During assembly the spring 71 is stressed so that the arcuate rib 76a is held with a substantial pressure against the ends of elevation and windage screws 73 and 74; thus it will be seen that the spring 71 holds the reticule support 40 and crosshairs 45 and 46 is a predetermined fixed position relative to the optical axis, and as a consequence the pendulum and its associated cant indicator are also indirectly held in position by the spring 71. Any movement of either the windage or elevation screws simultaneously efi'ects movement of the reticule and cant indicator without disturbing their- 36! Iclationship. In effect since the target image occuples substantially "the same optical plane as the reticule, adjusting 'screws 73 "and 74 provide a means to produce a relative displacement between the target image and reticule, and spring 71 maintains this displacement in a fixed position.

'It has been found that the thin walled telescope tube 68 acts as a diaphragm thereby amplifying the clicking noise resulting from the oscillating pendulum contacting the pendulum cage. To absorb this noise andto limit'the amplitude of the oscillative travel of pendulum 41, flexible fingers or pendulum stops 76 and 77 are provided. The fingers in this instance are of rectangular shaped thin material such as phosphor bronze or the'like material, and are bent downward to form equal angles with a horizontal plane passing through shaft 60. One end of each of the flexible fingers 76 and 77 is'sec ured to the pendulum and the opposite free ends are arranged to contact the inside wall of the bridging portion 61. 'This construction therefore assures the operator that there will be no clicking noises as would be the case if thependulum stops were inflexible.

In Figure 11 there is shown anothermodification of the cant-indicating member. In this instance a pendulum 80 has a weight 81 formed thereon in a manner herein described. A transparent tab 82, which should be relatively narrow, is secured to the-weightand the transparent tab 82 is formed, marked'or etched with a line 83 which may be utilized in the same manner as the glass filament 42 described hereinbefore. Since this tab, and consequently its indicia, is placed in a focal point of the optical system it is important that its area exposed to the light rays passing through the telescope be kept at a minimum; this is to insure minimum interference due to dust particles on the tab.

In Figures 13 and 14 there is shown another modified form of the indicating mechanism, wherein the pendulum cage 85 is formed from non-magnetic material such as synthetic resinous material. A U-shaped metal member 84 is disposed between the walls 85 and 87 of the enclosure, as shown in Figure '14, and is formed with an outer lamination of magnetic steel and an inner layer'of copper or the like material. With this construction the permanent magnet on the pedulum reacts with 'the'copper and magnetic steel structure so as to quench the oscillations of the pendulum in a manner described hereinbefore. It is to be understood that if the modification shown in Figure 12 is used, the telescope will be secured to the gun with conventional mounts for windage and elevation adjustments.

In Figure 7 the crosshair 45 and the filament 42 are in closely-spaced relation and are disposed so as to be'at'the focal point or" the objective lens. It is readily apparent that the closer the crosshair '45 and the filament 42, the

. greater the accuracy. The Vashaped notch construction described hereinbefore permits these elements to be in very closely-spaced relation. It is to 'be understood that the reference crosshair or reticule assembly 88 could be at the focal point of the ocular lens (see Figure 12) and the indicator could be positioned at the focal point of the objective lens, in lieu of being in closely-spaced relation as shown in Figure 7. With either of the described positions of the reticule and cant indicator or the reverse position of these assemblies the magnification-of the lens system visually indicates to the gunner eventhe very slightest amount of cant.

From the foregoing it can beseen-that I have provided a cant indicator which is simple to construct, easy to install, that is'positive in its indicating action, and one that insures the gunner absolute accuracy in so far as canting of the gun is concerned. It is to be understood that this invention may be'used in cameras, telescopes and other optical devices as well as in a telescopic rifle sight, and that the-embodiments shownin the telescopic 'rifiesight are forpurposes of illustration only.

his is a continuation -in part of my No. 699,487, filed September 26, 1946.

'I claim:

1. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, said objective lens having a focal point and said ocular lens having a focal point, mutually perpendicular crosshairs in said tube, one of said crosshairs being a horizontal crosshair, means for mounting said crosshairs in said field of view .to define a 'reticule at the focal point of one of said lenses, fixed bearing-support means mounted wholly within said tube and out of said field-of view, 'a pendulum mounted wholly within said tube and having a central opening permitting encirclement of said field of view said pendulum having spaced portions formed from resilient shock-absorbing material, said spaced portions being on opposite sides of said fixed bearing 'support means, said spaced portions being formed from light weight material of small cross-sectional area ,to permit ready flexing thereof, pivotal bearings acting between said bearingsupport means and said spaced portions formed from resilient shock-absorbing material on said pendulum defining a bearing support for said pendulum, a hairlike, elastic filament at said other focal point and having a free end and a fixed end, and means for mounting said hairlike filament to secure said fixed end to said pendulum and to have said free end extend partially across said opening, but short of said horizontal crosshair, to project into said field of view and to be in alinement with said pivotal bearings and said fixed end whereby said indicating member is in visual association with said reticule to indicate canting of the gun.

2. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted .lengthwise of said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, a reference cross-hair in said lens system, a weight in said tube at application Serial one side of said field of view, means on the opposite side of said field of view for pivotally mounting said weight for free-swinging movement thereof, a cant indicator on the same side of said field of view as said weight and having a fixed end and a free end, means for mounting said indicator on said weight to have said fixed end secured to said weight and to have said free end extend across said field of view for association with said reference crosshair to indicate canting of said gun, and resilient means acting between said weight and said pivotal mounting means to absorb shock due to recoil of said gun'whereby to prevent damage to said'pivotal mounting means.

3. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of. said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, a vertical crosshair insaid tube, a weight in said tube at one side of said field of view, a cant indicator on the same side of said field of view as said weight and having a fixed end and a free end, means for-mounting said indicator on said weight to have said fixed end secured to said weight and to have said free end extend partially across said field of view, and weight support means on the opposite side of said field of view from said weight for pivotally mounting said weight to permit said indicator to swing transversely of said tube for visual association with said vertical crosshair, said last mentioned means including at ,least one arm portion formed from relatively thin material having a small cross-sectional area to permit flexing thereof and operable to absorb shock due-to recoil of said gun.

4. In an optical device for indicating canting of a gun the combination of an elongated-tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, a reticule having a reference crosshair, means for fixedly mounting said reticule in said tube to permit magnification of said crosshair, a weight in said tube at one sideof said field of view, means on the opposite side of said field of view for pivotally mounting said weight for free-swinging movement thereof, a cant indicator having a fixed end and a free end, means for mounting said indicator on said pendulum above said weight to have said fixed end secured to the weight and said free end extend partially across said field of view to be in alinement with said pivotal mounting means and said fixed end of said cant indicator for visual association with said reference crosshair, and at least one'relatively thin, flexible, arcuate arm extending between said pivotal mounting means and said weight to support the latter, said arm having a relatively thin cross section and passing at one side of said field of view and forming a shock-absorbing means to prevent damage to the pivotal mounting means due to the recoil of the gun.

S. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, a vertical reference crosshair in said tube, a weighted pendulum in said tube at one side of said field of view, means on the opposite side of said field of view for pivotally mounting said weighted pendulum for free-swinging movement thereof, a cant indicator having a fixed end and a free end, means for mounting said indicator on said pendulum to have said fixed end secured to the pendulum and said free end extend partially across said field of view to be in alinement with said pivotal mounting means and said fixed end of said cant indicator for association with said reference crosshair to indicate canting of said gun, means out of said field of view, for interconnecting said pivotal mounting means and said weighted pendulum, and resilient means integral with said pendulum co-acting with said tube to limit the amplitude of the pendulum oscillation and to minimize engagement of the pendulum with the tube and the attendant noise resulting therefrom.

6. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of a gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, a reticule having a reference crosshair, means for fixedly mounting said reticule in said tube, a weight in said tube at one side of said field of view, means for pivotally mounting said weight for free-swinging movement'thereof including magnetic circuit means adjacent said weight, a .cant indicator having a fixed end and a free. end, means for mounting said indicator on said weight to have said fixed end secured to the weight and said free end extend partially across said field of view to be in alinement with said pivotal mounting means and said fixed end of said cant indicator for visual association with said reference crosshair to indicate canting of said gun, means in said tube and outside the field of view for interconnecting said pivotal mounting means and said weight to provide a support for the latter, and magnetic means acting between said weight and said magnetic circuit means to quench the oscillation of said pendulum whereby to permit the detection of a minute amount of cant of said gun.

7. The combination recited in claim 6 wherein the magnetic means include a permanent magnet attached to the weight and an electrical conductor intersecting the flux of said permanent magnet.

8. The combination recited in claim 11 wherein the magnetic means include a permanent magnet, a soft ferromagnetic material positioned in the magnetic field of said permanent magnet, and a low-resistance electrical conductor interposed between the soft ferro-magnetic material and the permanent magnet for the generation of ddy currents.

9. In combination with a telescopic gun sight having a tube, a cant indicator located wholly within the tube of the gun sight, said cant indicator including means for attaching it to the gunsight tube on the interior thereof without affecting free vision through the gun sight, a tubular reticule cage having sighting means attached thereto and having a transverse slot, a pendulum oscillatable within the slot, a pivot supporting the pendulum at its upper end within the cage, a radially extending cantindicating member rigidly secured to the pendulum and extending across the line of sight through the gun sight and thereby being visually associated with said sighting means to permit correction of the cant of a gun carrying said telescopic sight, said pendulum being shaped like a ring and having a permanent magnet at its lower enlarged end, the cage being of such material and being so close to the magnetized pendulum that eddy currents will be set up in the cage to quench oscillations of the pendulum.

- 10. In combination with a telescopic gun sight having a tube, a cant indicator located wholly within the tube of the gun sight, said cant indicator including means for attaching it to the gun sight tube on the interior thereof without aifecting free vision through the gun sight, a tubular reticule cage having sighting means attached there to and having a transverse slot, a pendulum oscillatable within said slot, a pivot supporting the pendulum at its upper end within the cage, a radially extending cantindicating member rigidly secured to the pendulum and extending across the line of sight through the gun sight and thereby being visually associated with said sighting means to permit correction of the cant of a gun carrying said telescopic sight, said cage being of material capable of permitting eddy currents to flow, and said pendulum including a permanent magnet with poles on opposite sides to set up eddy currents when it oscillates within said cage.

ll. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, said objective lens having a focal point and said ocular lens having a focal point, mutually perpendicular crosshairs in said tube, means for mounting said crosshairs in said field of view to define a reticule at the focal point of one of said lenses, fixed bearing-support means mounted Wholly within said tube and out of said field of view, a pair of downwardly curved arms mounted on said bearing means, said arms extending around one side of the field of view and being formed from relatively thin, flexible, light weight material having a relatively small cross-sectional area to absorb shock, pivotal bearing means in said tube for mounting said downwardly curving arms on said fixed bearing support, a pair of upwardly curving arms on the opposite side of said field of view and interconnected respectively with said downwardly curving arms, a cantindicating member in said tube and mounted at said other focalpoint and having a free end and a fixed end, and means in said tube for securing said fixed end to an intermediate portion of said upwardly curving arms to have said free end project into said field of view and adapted to be in visual association with one of said crosshairs as a reference line whereby to indicate canting of said gun.

12. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, said objective lens having a focal point and said ocular lens having a focal point, mutually perpendicular crosshairs in said tube defining predetermined reference lines, means for mounting :said crosshairs in said field of view to define a reticule at'the focal point of .one of saidlenses, weight means in said tube at one side of saidfield of view and positioned at one of the focal points of said lens system, fixed bearing means in said tube on the opposite side of said field of view, resilient shock-absorbing means in said tube out of the field of view interconnecting said weight means and said bearing means, a cant-indicating member in said tube at one of said focal points having a free end and a fixed end, and means in said tube for mounting said cant-indicating member to secure said fixed end to said weight means and to have saidfree end project into said field of view and adapted to be in visualassociation with one of said crosshairs to indicate canting of the tube and the gun from one of said predetermined reference lines.

13. The combination recited in claim 12 in which said cant-indicating member comprises a transparent member having a relatively thin, narrow section, and having an indicia thereon for visual association with one of said crosshairs to indicate tilting of the gun.

14. The combination recited inclaim '12 in which said cant-indicating member comprises a hairlike filament formedfrom glass.

15. In an optical device for indicating canting of a gun, the combination of an elongated tubeadapted to be mounted lengthwise of said gun, spaced lenses in said tube including objective lenses andvocular lenses defining an optical lens system having a field of view, at least one of said lenses being a magnifying'lens, a reticule having a reference crosshair, means for fixedly mounting said reticule in said tube to permit magnification of said crosshair, weight means, means for mounting said weight means permitting free swinging movement thereof transversely of the longitudinal axis of said tube, said last mentioned means havingportions formed from relatively thin, light weight material having a relatively small crosssectional area to be resilient under shock, a cant indicator having a fixed end and a free end, means for mounting said indicator on said weight means to have said fixed end secured thereto and said free end extend across said field of view in alinement with said weight-support means and said fixed end of the cant indicator for magnification and visual association with said reticule whereby canting of said gun is visually observed by the relative positions of said referencecrosshair and said cant indicator.

16. In an optical device for indicating cant of a gun the combination of a tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube, including objective lenses and ocular lenses defining an optical lens system having'a field of view, said objective lenses having a focal point and said ocular lenses having a focal point, at least one reference hair in said tube, means for mounting said reference hair in said field of view to define a reticule in the focal point of one of said lenses, fixed bearing support means mounted wholly within saidtube and out of said field of view, a pair of downwardly extending arms extending around-one side of the field of view, pivotal bearing means in said tube and intermediate said arms for mounting said arms on said fixed bearing support, a pair of upwardly extending arms on the opposite side of said field of view and interconnected with said downwardly extending arms, a cant indicating member in said tube mounted in the focal point of one of said lenses and having a free end and a fixed end, means in said tube for securing said fixed end to an intermediate portion of said upwardly extending arms to have said free end project into said field of view and adapted to be in visual association with one of said reference hairs as a reference line to indicate canting of said gun, and means independent of said pivotal mounting means mounted on one of said pair of arms and coacting with said fixed bearing support means for limiting the amplitude of movement of said arms.

17. In an optical device for indicating cant of a gun the combination of a tube adapted to be mounted lengthwise of said gun, spaced lenses-in said tube, including objective lenses and ocular lenses defining an optical lens system having a field of view, said objectivelenses'havin-g a focallpoint and said ocular lenses having a focal point, at least one reference hair in said tube,means for mounting said reference hair in said field ofview to definea reticule in the focal point of one of said lenses, fixed hearing support means mounted wholly within said tube and out of said field of view, pivotal bearing means mounted on said fixed bearing support means, 'at 'least one arm mounted on and extending downwardly from said pivotal bearing means, said arm being shaped to extend around one side of the field of view, a second arm onthe' opposite side of said field of view interconnected with said down-' wardly extending arm to define-a pendulum, a cant indicating member in said tube and mounted 'at'thefocal point of one of said lenses and having'afree'end and a'fixed end, means in said tube for securing-said fixed end'to said second arm to havesaid free end project into said field of view and adapted to be in visual association with said referencehair asa reference lineto indicateicanting of said gun, and means independent of said pivotal bearing means mounted on said downwardly extending arm and coacting with said fixed bearing support to limit the amplitude of movement of said arms.

18. In an optical device for indicating cant of a gun the combination of a tube adapted to be mounted lengthwise of said gun, spaced lenses in said tube, including objective lenses and ocular lenses definingoan optical lens systemhaving a field of view, said objective lenses having a focal point and said ocularlenses having a focal point, a reference hair in said tube, means for mounting said reference hair in said field of view to define a reticule in the focal point of one of said lenses, fixedbearing support means mounted wholly Within said tube and out of said field of view, a pair of downwardly extending arms extending around one side of the field of view, pivotal bearing means in said tube for mounting said downwardly curving arms on said fixed bearing support, a pair of upwardly extending arms on the opposite side of said field of view and interconnected with said downwardly extending arms, a cant indicating member inisaid tube mounted at one of the focal points and having a free end and a fixed end, means in said tube for securing said fixed end to an intermeditae portion of said upwardly extending arms to have said freeend project into said field of view and adapted to be in visual association with said reference hair as a reference line to indicate canting of said gun, aweight formed from magnetic material mounted on said upwardly extending arms to define a pendulum, and means adjacent said weight and .operative in response to movement thereof to dampen the oscillatory motion of the pendulum and said cant indicating member.

l9. In an optical device for indicating cant of a gun the combination of a tube adapted to be mounted "lengthwise of said gun, spaced lenses in said tube, including objective lenses and ocular lenses defining an optical'lens system having a field of view, said objective lenses having a focal point and said ocular lenses having a focal point, a reference hair in said tube, means for mounting said reference'hair in saidfield of v'iew'to define aret'icule in the focal point of one of said lenses, fixed bearing support means mounted wholly within said tube and out of said field of view, at least one arm mounted on and extending downwardly from said bearing support means, said arm being shaped to extend around one side of the field of view, pivotal bearing means for mounting said downwardly extending arm on said fixed bearing support, a second arm on the opposite side of said field of view interconnected with said downwardly extending arm to define a pendulum, a Weight attached to said second arm formed from magnetic material, a cant indicating member in said tube and mounted at one of said focal points and having a free end and a fixed end, means in said tube for securing said fixed end to said second arm to have said free end project into said field of view adapted to be in visual association with said reference hair as a reference line to indicate canting of said gun, means independent of said pivotal mounting means mounted on said downwardly extending arm coacting with said fixed bearing support to limit the amplitude of movement of said arms, and means adjacent said weight and operative in response to movement thereof to dampen the oscillatory motion of the pendulum and said cant indicating member.

20. In an optical device for indicating canting of a gun the combination of an elongated tube adapted to be mounted lengthwise of a gun, spaced lenses in said tube including objective lenses and ocular lenses defining an optical lens system having a field of view, a substantially circular reticule support mounted within said tube, a reticule positioned at the focal point of said optical lens system and held in place by said reticule support, a weight, means for flexibly and pivotally mounting said weight wholly within said tube for free transverse swinging movement relative to said tube, said weight and its flexible mounting means being entirely out of the field of view, a cant indicator per se mounted wholly within said tube and positioned for visual association with said reticule, said cant indicator per so being oscillatable transverse to said tube in response to said swinging weight and positioned in the focal point of said optical lens system thereby in effect projecting the relative position of the cant indicator per se and reticule into space for an infinite distance; and spring means in said tube to hold the reticule support, the reticule and cant indicator per se in a predetermined fixed position relative to the optical axis when the weight is at rest.

21. The combination recited in claim 20 with adjustable means mounted on said tube for selectively moving said reticule support bodily in directions substantially at right angles to each other.

22. In an optical device to indicate canting of a gun, the ,combinaton of a tube adapted to be mounted lengthwise of the gun, an optical lens system having an optical axis and mounted in said tube, said system comprising an objective lens, an erecting lens and an ocular lens mounted in said tube; a reticule mounted within said tube and rigidly held thereby; a pendulum fully enclosed in said tube and out of the field of view of said optical system, said pendulum having at least one portion formed from thin, light weight material of reduced cross-sectional area and adapted to be flexible When subjected to shock means for mounting said pendulum in said tube for oscillative travel transversely to the optical axis of said optical lens system; and a cant indicating member attached to said pendulum and extending radially into said field of view for visual association with said reticule; said cant indicating member and said reticule being positioned in the optical system for optical magnification and being simultaneously in focus when viewed through said ocular lens of said optical lens system thereby permitting the detection of a minute amount of cant of said gun.

23. In a mechanism to indicate canting of an optical device the combination of at least one optical lens having a field of view, a housing for said lens, means providing a reference point projecting into said field of view and supported by said housing in predetermined relation therewith, a pivotally mounted pendulum out of said field of view and supported by said housing for oscillative movement transversely to the optical axis of said lens, a cantindicating member mounted on said pendulum to be movable therewith and extending into said field of view for visual association with said reference point means, said cant-indicating member and reference point means aligning in the normal position of the parts and when not in alinement indicating the cant of the housing when rotated clockwise or anti-clockwise in a plane transverse to said optical axis of said lens whereby the operator may adjust the tilt of the housing to bring the reference point means and the cant indicator into alinement, and magnetic means including means to effect the generation of electrical eddy currents associated with said pendulum to quench the oscillation of said pendulum, thereby permitting the operator to adjust the housing to correct for minute amounts of cant of said housing in a short period of time.

24. In a mechanism to indicate canting of an optical device the combination of at least one optical lens having a field of view, a housing for said lens, means providing a reference point projecting into said field of view and supported by said housing in predetermined relation therewith, a pendulum out of said field of view, means for mounting said pendulum within said housing including a shaft having pointed ends and substantially parallel with the optical axis of said lens whereby to permit oscillative movement of the pendulum transversely to the optical axis of said lens, conical bearings supporting the ends of said shaft, means for mounting said bearings in said housing on opposite sides of said pendulum, including magnetic circuit means adjacent said pendulum, a cant-indicating member mounted on said pendulum to be movable therewith and extending into said field of view for visual association with said reference point means, said cant-indicating member and reference point means alining in the normal position of the parts and when not in alinement indicating the cant of the housing whereby the operator may adjust the tilt of the housing to bring the reference point means and the cant indicator into alinement, and magnetic means acting between said pendulum and said magnetic circuit means to quench the oscillation of said pendulum.

References Cited in the file of this patent UNITED STATES PATENTS 126,372 Barnum May 7, 1872 476,874 Cummins June 14, 1892 499,160 Cummins June 6, 1893 502,433 Gibboney Aug. 1, 1893 1,009,148 Hoffman Nov. 21, l9l1 1,135,787 Grauheding Apr. 13, 1915 1,533,723 Brown Apr. 14, 1925 2,243,793 Cummins May 27, 1941 2,275,631 Johnson Mar. 10, 1942 2,452,592 Meyer Nov. 2, 1948 FOREIGN PATENTS 847,490 France July 3, 1939 

